Hidden-metal detector



S. HERR July 31, 19280 1,679,339

HIDDEN METAL DETECTOR Filed Feb. 1924 mvsm'ora hirl Herr,

BJ Q7 M Art-0m e Patiented July 31, 1928.

2 UNITED STATES 1,679,339 PATENT OFFICE.

SHIQRL HERB, OF CBAWFORDSVILLE, INDIANA.

HIDDEN-METAL DETECTOR.

Application filed February 4, 1924. Serial No. 690,360.

My invention consists of an improvement in hidden metal detectors, and the primary object of the invention is to provide portable means of locating submerged, buried or hidden metallic objects by the production of sound waves efi'ected through distortion of a magnetic held by reason of the object coming within the lield. A. further object of my invention resides in the simplicity of its construction such that the device is efi'ective with a single primary winding and a single secondary winding. I accomplish these and such other objects as may hereinafter appear by the means shown more or less diagrammatically in the accompanying drawing, in which Fig. 1 is a plan view of the detector illustrating the wiring diagram and the relation of the primary and secondary windings; Fig. 2, a vertical section taken on the line 2-2 of Fig. 1; and Fig. 3, a vertical section taken on the line 3-3 of Fig. 1.

Like characters of reference indicate like parts throughout the several views.

About an iron pole-piece 5, I wind the primary winding 6 which has one terminal connected by the Wire 7 to a storage battery 8. The wire 9 leading from the other terminal of the primary winding 6 is connected to an automatic contact breaker of usual and well known construction, comprising the armature core 10, about which the wire 9 is wound, the vibrating spring member 11 having the contact point 12 in circuit with the wire '9 leading from the core 10, and the stationary point 13 adapted to be contacted normally by the point 12. The stationary point 13 is in turn connected to the other terminal of the storage battery 8 by the wire 14. \Vith the circuit completed as above described, the points 12 and 13 will rapidly break and make contact such that the current flowing through the primary winding 6 is of pulsating nature which sets'up a corresponding magnetic field about the winding 6 and its pole-piece 5.

The pole-piece 5 is supported by the ties 15 bearing on the cross members 16 carried by the frame 17' of non-metallic material such as wood, about which iswrapped the secondary winding 18, so held at an appreciable distance from the polepiece 5 and its winding 6. The two terminals of the secondary winding 18 are, connected to a telephone receiver 19 of usual and well known construction.

The polepiece 5 is provided with the slots 20 to receive the ties 15 and the top wedges 21 and 22 and the under wedges 23 and 24.

detector requires an initial adjustment of t e wedges 21, 22, 23, and 24 such that the pole-piece 5 and its winding 6 ma be so located within the secondary win ing, and there secured that no sound is heard from the receiver 19. With the use of wedges the pole-piece may be tilted, moved up or down, or horizontally to obtain the proper location in respect to the secondary winding 18. When the detector is carried about in an attempt to locate the object sought, the receiver 19 is held to the observers ear, and no sound is heard until a metallic object is brought within range of the magnetic field set up by the primary winding 6, when the presence of such an ob ect will so disturb the magnetic field as to permit the induced current in the secondary winding 18 to cause the telephone receiver 19 to emit a distinct sound.

The range within which the detector must be brought to the object sought, I find to be from four to six feet with my present 7 construction, but this may be varied by varylng the current and the relation and proportion of primary and secondary windings. Having fully described my invention in the form now best known to me, I desire to set forth that the structure is ca able of variations without departing from t e spirit of the invention, and I therefore do not desire to be limited to the precise form as shown, nor any more than may be required by the following claims. l

I claim: 1. In a metal detector, the combination with a source of electric current, an automatic vibrating contact breaker, and a telephone receiver, of a pole-piece, a primary winding on said pole-piece in electrical circuit with said source of electric current and said contact breaker, a frame supporting said ole-piece, and a secondary winding Woun about the periphery of said frame, said secondary winding being at ri ht anglee to and being at a substantial istance rom' said primary winding and being in electrical circuit with said telephone receiver. 2. In a metal detector, the combination with a source of electric current, an automatic contact breaker, and a telephone receiver, a pole-piece, a primary winding on said pole-piece in electrical circuit with said source of current and said contact breaker, a non-metallic frame centrall supporting said pole-piece, and a secondary winding surroundin said primary winding mounte on the sai frame at a substantial distance from said primary winding and such that the axis of the secondary winding is normal to the axis of the primar winding magnetic field, and electrical con. uctors placing said telephone in electrical circuit with the seconda winding.

3. 31 a metal detector, the combination with a source of electric "current, an automatic vibrating contact breaker, and a telephone receiver, of a pole-piece, a primary winding on said pole-piece in electrical circuit with said source of current and said contact breaker, a frame supportin said pole-piece, a secondariy winding woun about the eriphery of sai frame, said secondary win ing being at right angles to and being at a substantial distance from said primary windin and being in electrical circuit with said te ephone receiver, and means of adjustably securing said pole-piece in said enses frame centrally of said secondary winding.

4. In a metal detector, the combination with a source of electric current, an automatic contact breaker, and a telephone rcceiver, of a pole-piece, a primary winding on said pole-giece, conductors placing said primary win ing in circuit with said source of current and said contact breaker, a frame supporting said pole-piece, cross member; 1n said frame, ties between said cross members, a plurality of wedges on and under said ties engaging with said pole-piece, a secondary winding surrounding said primary winding mounted on said frame, said secondary winding being at a substantial distance from said primary winding and being normal to the primary winding, and electrical conductors lacing said telephone receiver in circuit with said secondary windi ed at Ci'awfordsville, in the county of L ontgomery and State of Indiana, this 1st day of February, 1924.

SHIRL HERB. 

